Synchronizing system



Sept. 23, 1941. s. w. SEELEY 2,256,530

SYNCHRONIZING SYSTEM Filed Oct. 6, 1938 2 Sheets-Sheet l 43 J- FILTER(AUTOMATIC CPI/ASE FREQUENCY asrscron CONTROL UNIT 01/ T PU T 70TRANSMITTER INVEN TOR. STUART WJ'EELEY ATTORNEY.

Sept. 23, 1941. s. w. SEELEY SYNCHRONIZING SYSTEM Filed Oct. 6, 1938 ZSheets-Sheet 2 9523M a 55m I NV EN TOR. STUART m SEELEV A TTO RN E Y.

Patented Sept. 23, 1941 SYNCHRONIZIN G SYSTEM Stuart W. Sceley, Baysidc,N. Y., assignor to Radio Corporation of America, a corporation ofDelaware Application October c, 1938, Serial No. 233,553

6 Claims.

The present invention relates to television systems and is particularlydirected to a system for controlling the production of the so-calledoddline type of interlaced television images. The invention also relatesgenerally to circuits for controlling the repetition of such types ofproduced television images in receiver apparatus so that the receivedimage is at all times properly and adequately synchronized and thespacing between the lines of each field of the interlaced imagesaccurately maintained in constant relationship.

In its fundamental form the invention, as it is to be described herein,includes a suitable form of oscillator from which is developed orproduced oscillatory electrical energy of a substantiallyv the supplycircuits.

is produced from successive halves of like polarity of the developedsine wave energy a series of electrical impulses which are caused tobecome recurring at repetition frequency of each line of the picture. vinvention means are also provided to derive from Further, as a part ofthe the developed sine wave energy further successions of uniformimpulses which are caused to occur at twice the frequency and repetitionrate of the line synchronizing impulses.

The invention further contemplates making suitable provision forcombining all of these serval forms of different frequency in a propersequency to form a complete chain of control impulses which serve tosynchronize the line and field repetition rates of a received televisionimage reproduction. I

In the July 1938 issue of Electronics there is described on pages 28, 29and 55 a certain form According to the presently used methods oftransmitting television-signals television pictures of 441 lines areproduced. These television pictures are repeated at the rate of 30picture frames per second. However, because of a desire to interlace theproduced pictures, in order that the flicker may be substantiallyreduced, each picture frame is transmitted in the form .of two picturefields, of 220 lines each with a result that the transmitted fieldfrequency is picture fields per second. This particular field frequencyis quite desirable because it permits interlocking the field repetitionfrequency with the usual power supply frequency of 60 cycles per second.Proper synchronization and interlock of the field frequency and thepower supply frequency reduces hum bands in the received picture whichmight result from ripple in the deflection and The interlacing of thevarious picture fields one withthe other occurs as a natural consequenceof the non-integral relationship between the field repetition frequency,herein assumed as 60, and the line repetition frequency herein assumedas 13230. (this being formed from picture fields of 441 lines eachrepeated 30 times per second.

As was explained, however, in the Electronics publication, herein abovereferred to, during the time period when the field patterns are changingin the interlacing operation and during the vertical synchronizinginterval a special form of signal is transmitted in order that thehorizontal synchronism may not be lost and it is further an object ofthe present invention to provide ways and means for producing thesesignals and further to provide for controlling the time period when theybecome efiective in the transmission.

Other objects of the present invention are to provide a greatlysimplified arrangement for transmitting synchronizing signals whichshall cause television images to be repeated at the desired frame andfield repetition rates for a given number of picture lines and also toprovide for the production of synchronizing signals which shall followin proper time relationship the complete train of image signals whichresult from scanning the subject of which the'electro-optical imageis tobe produced on the viewing instrument.

It is a still further object of my invention to provide an improved formof pure electronic type of generator for generating the above describedforms of impulses which shall be used at receiver points forsynchronization of television images. I

A further object. of my invention is to provide frequency doubler.

an improved method of and means for controlling, delaying, shifting orotherwise determining the time at which such produced electricalimpulses shall become effective in the transmitting circuits.

Further objects, features and advantages of my invention, of course,will become apparent and.

at once familiar to those skilled in the .art to which the invention isdirected by reading the following specification and claims in connectionwith the accompanying drawings, wherein:

minal 52.

Fig. 1 diagrammatically illustrates one form pulses of the typehereinabove described; and wherein Fig. 2 illustrates schematically thewave form of the several impulses which result from the operation of thecircuit of Fig. 1.

- of arrangement and circuit for producing the im- Referring now to thedrawings there is provided an electronic oscillating tube II which maybe of the general type known in the art as the 6A8 which is adapted togenerate electric oscillations of sine wave formation at a frequencyassumed to be 13230 cycles for a 441 line television picture to berepeated thirty times per second. The tube includesa cathode |3,a No. 1grid I5, and a No. 2 grid H which electrodes cooperatively function as afirst part or section of the tube which is termed the oscillatorsection. In addition, there is provided within the tube II a No. 4 gridl9 and a No. 5 grid 2|, as well as the usual output electrode or anode23. The'oscillating portion of the tube includes the cathode l3 and theNo. 1 and 2 grids l5 and II,

respectively, of which the latter serves as an anode or output element.These grid elements are connected to the terminals of a tuned circuit 25comprising the inductance element 21 and the two capacity elements 29and 30 of which one or both may be variable. The capacity elements 29and 30 are serially connected and the junction point is connected toground (or fixed potential) at 3| as indicated. The series connected capacity elements 29 and 3| are shunted by the inductance element 21 sothat with the N052 grid connected by way of the conductors 32 and 33 toone end of the resonant circuit 25 and the N0. 1 grid connected by wayof the conductors 34 and 35 through the capacity element 36 to the otherend 31 of this tuned circuit 25 oscillations will be developed whensuitable energy is supplied to the tube Such operating energy issupplied by way of the choke coil 38 connected to a source of positivepotential at the terminal 39 and bias voltage is supplied. to the No. 1grid l5 by way of the bias resistor 4| connected to ground.

The connection of the oscillatory circuit immediately above described isessentially a form of the well known Colpitts oscillator so that withsuitable operating potentials applied there will be generated ordeveloped in the tuned circuit 25 electrical energy of a frequencydetermined by the circuit constant and of a sine wave characteristic.Electrica energy of a frequency double that appearing in the circuit 25can be developed 'in the output section of the tube II by connecting thetube (as indicated) so thatit operates as a In the form in which thetube is connectedthe tuned tank circuit 43, comprising the inductance'44and the capacity 45 (variable, if desired), is tuned totwice thefrequency of the tuned circuit 25. This tuned circuit 43 is c'onnectedbyway of the coupling condenser I4 1 at one end to the anode element 23 ofinterlacing with the line frequency (that frethe tube II and at theother end to ground at 3| by way of the conductor 48 and then also byway of the conductor 49 and the coupling condenser 50 back to theelectrode 2| of the tube ll.

Suitable anode voltage for the tube II is supplied by way of theresistor 5| connected to ter- Operating voltage forthe electrode 2| issupplied by way of the terminal connection 53 and the electrode I9 isoperated at cathode potential by way of the connection to ground at 54'.In view of the well recognized desire to develop the synchronizingimpulses to initiate the frequency division which is finally to equalthe field frequency from the same source that develops the linesynchronizing controls, it is desirable that energy of double thefrequency of the initially developed oscillations shall result in orderthat ultimate frequency division shall be equal to the field frequencydesired. This is substantially due to a condition imposed by theodd-line quency developed in the tuned circuit 25) shall constitute noharmonic of the field frequency and further that the second harmonic ofthe, line frequency which appears in the tuned circuit 43 shallconstitute no even harmonic of the field frequency.

Accordingly, as is well known in the art and as has already beenexplained in the patent of John Paul Smith, No. 2,132,654, issued Oct.16, 1938, frequency division of the double frequency appearing in thetuned circuit 43, which is at twice the frequency which appears in thetuned circuit 25, may be divided by a chain of stabilizedmulti-vibrators. Such a chain of multi-vibrators may, where it is,assumed that the system is operating to produce a 441-line picturerepeated at picture fields per second, comprise three separatemulti-vibrator stages 51, 58 and 59 where the output from themulti-vibrator stage 51 will be equal .to

where F is the frequency of the fundamental or the frequency developedand appearing in the tuned circuit 25. This output is then fed to thesecond multi-vibrator stage 58 whose output is 'equal to Y and likewisethe output from this multi-vibrator stage is fed to a thirdmulti-vibrator 59.whoscmulti-vibrator 59 through a suitable form ofdetector, such as a phase detector to which is also supplied energy ofthe power supply frequency. wherein the phase "of the developed energyis compared with the phase of the 60 cycle power supply frequency. Theoutput .of such a phase detector may be through a suitable form offilter network and thence to an automatic frequency control unit ofknown character to control or stabilize the frequency of the oscillatorl I. How.

ever, such a control feature is not specifically a part of the presentinvention, and, therefore, it is desirable to consider a second portionof the output of the multi-vibrator 59 which is to control the timingand wave shaping units which shall produce the synchronizing signals ofthe form indicated by Fig; 2 of the drawings.

For this purpose, there is coupled to the inductance element 21 of thetuned circuit 25- a coupling coil 6| having one terminal thereofgrounded by conductor 82 at ground'3l and the other terminal thereof isconnected by way of conductor 83 to be supplied to a suitable form ofrectifier element such as the push-pull rectifier 85. The other portionof the output multi-vibrator 59 is -then supplied by way of conductor 55to control, in a manner later to be described, the keying of thehorizontal synchronizing impulses in the'output of the wave shaping unitconnected with the output of the rectifier 65.

It was above explained that the oscillatory energy for developing thesynchronizing impulses was in the form of sine wave energy since it wasrelatively easy accurately to control and stabilize an oscillator todevelop sine wave energy as contrasted with units, such as uncontrolledmultivibrators and the like, to develop energy of an impulse form.

According to the form of transmission now most commonly usedexperimentally, it has been found that the duration ofv thesynchronizing interval occurring at the end of each picture field shallbe of the order of 7% of a of a second. Accordingly, the synchronizingcontrol which shall control the vertical motion of the cathode ray beamused to reproduce the teleyision picture must become effective duringthis time period and, in ,some sense, of course, provision must be madeso that the horizontal synchronizing control does' not cease operatingduring such time period. Uniess a very definite interlock is to beobtained, asa practical matter, due to the return time during thereproduction of each picture field being a relatively large percentageof the time required to reproduce each picture field,

there might result .a substantial drift in horizontal line production ofthe initial portion, at 7 least, of each produced picture. Hence, by thearrangement described herein the sine wave energy developed at linefrequency and derived by way of the coupling coil 8| from the tunedcircuit 25 iscaused to pass through the wave shaping unit connected tothe output 'of the rectifier 65 and therein be so modified by theso-called clipping, integrating, differentiating and keying processes,which will be later described herein, in order to produce the desiredform of control signal.

In this form of apparatus the line frequency sine wave energy suppliedfrom the tuned circuit 25 through conductor 63 is applied to each halfof the tube 65 (which tube may beone of the type known in the ,art astype 6H8) in phase opposition through the transformer 6'! having itsprimary'winding 88 shunted, for tuning purposes if'desired, for purposesof symmetry in each half of the ware, by a condenser 89 connected toground at 18 and having its secondary winding H center-tapped to groundin the usual manner by way of the conductor 12. The anode elements 13and 14 of the double diode 65 are connected respectively to the controlelectrodes 15 and 18 of wave shaping tubes 11 and 18. It is quitedesirable in such a connection, however, that the half of the secondarywinding 1| of the transformer which is connected between the cathodeelements 19 and 88 of the two halves of the tube be accurately balancedwith respect to ground 18 and for this purpose the winding 'II shouldpreferably be bifilar and the core of the transformer 61 should be suchthat it does not show excessive loss at the assumed line frequencysupplied through the conductor 83.

Connected between the control electrodes I5 and 16 of the tubes TI andI8 and the cathode elements thereof are the usual diode resistors 8| and82. The voltages which appear across these diode resistors 8| and 82 arenegative in sign so that when rectified half wave portions of the energyin conductor 63 are impressed upon the tubes l1 and 18 (which tubes arepreferably, although not necessarily, tubes of the type known in the artas the type 1851) the control electrodes l5 and 16 will be driven wellbeyond a cut-off potential so as to clip in this way the two alternatehalf waves.

It is frequently desirable, however, to vary the cut-off voltage on thetubes IT and I8 and hence the so-called screen electrodes 83 and 84 areprovided with an adjustable screen potential through their connection byway of the conductor 85 to the resistor element 86 as indicated. Thisform of arrangement permits a variation of the width of the clipped halfwaves.

Anode or plate potential for the tubes 11 and I8 is provided by way ofthe plate resistors 81, 81' from suitable voltage sources (not shown)connected to the free end of each of the anode resistors. The outputenergy from the tube 11 is supplied in parallel to a pair of tubes 88and 89 respectively through suitable conductors 90 and 9| and thecoupling condensers so as to be impressed in parallel upon the controlelectrodes 92, 93 of these. tubes. The output energy from the tube 88 isfed by Way of the resistance coupling to a further wave shaping tube 95.Output from this tube is then fed to a keying tube,9l, later to bedescribed.

Similarly, the output of the tube 89 is fed to tube 18 is supplied uponthe control electrode l8l of a wave shaping tube I82 of a generallysimilar characteristic to the tube 88 connected to receive the output ofthe first wave shaping tube 17. The tube I82, it will be seen, has,together with the tube 89, a mutual plate or anode resistor I83 throughwhich operating potentials are supplied. With the connection shown theoutput energy from the tube I82 is also supplied to the controlelectrode I88 of the tube 98 by way of the coupling condenser 99 and theconductor I84. In addition, the output energies from the tubes 89 andI82 are also combined by way of the conductor I'M and a couplingcondenser I86 to be impressed upon the control electrode I81 of a waveshaping tube I88.

It will thus be seen from what has been above 8 described that there isimpressed upon the tubes 88 and 95 impulses of rectified currentoccurring at the line frequency corresponding to the frequency of thesine wave energy generated in the oscillator portion of tube II andappearing in the tuned. circuit 25. Upon the tubes '98 and I88 there isproduced the combined output of tubes l1 and 18 so that in the output ofthe tubes 98 and I88 there results relatively square bottom pulses of afrequency double that which is impressed upon the rectifier tube 55through the transformer 61. :Theoutput energy from the tubes 90 and I issupplied to additional keying tubes I I0 and H2, later to be describedin more detail.

In general, the wave shaping channel including and capacity in these twochannels are chosen of somewhatdifferent value from that, in whichincluded tube I08 so that the re'sultantfimpulses which are. supplied tothe control electrodes of thekeying tubes I I0 and H2 shall, in the oneinstance, be of relatively long duration V the frequency divider ormulti-vibrator '59, which is supplied by way' of the conductor 55, itwill. be noted that this output energy is impressed .in parallel uponthe..tubes H3 and H4 by way of the suitable coupling condensers. Througha suitable choice of resistance and capacity elements H5, H6 and II1ytheimpulse which is upplied tothe control electrode IIB of the tube H3 isdelayed for a short time period which is equal to the equalizing pulseinterval (see Fig. 2) immediately following the last line of picture orvideo signals and occurring prior to the time when the verticalsynchronizing pulses appear. The output energy from-the tube 3 is thenfed by way of the resistance coupling connection,

- the tube 98 is similar to that channel including the tube I00, exceptthat the values 0f resistancequency are impressed upon the controlelectrode I of the tube II4 substantially without delay, as contrastedto the delay introduced in the application of these impulses upon the.tube H3. The output energy from the tube H4 is fed by way of thecoupling condenser I 21 to the con-- trol electrode I28 of an invertingtube I29 whose output is, in turn, coupled to the input of a tube I30 byway of a coupling condenser I3l so as to" be impressed upon the controlelectrode I32 of the tube I30; The output energy from the tube I30 is.supplied in parallel upon the control elec- I, trodes m and I35 of apair of tubes I31 and I38 of which the'latt'er functions, as will behereinafter explained, as a tube for'keying one of the series ofimpulses resulting from the rectification of the sine wave energydeveloped by the tube II at line frequency and supplied to the rectifier55. Those impulses which are fed from the output of the tube I 30 to thetube I38 are passed by way of the condenser I40 to the con-.

".trol electrode I35 thereof.

comprising the usual output and leak resistors It will be seen that thetube I38 serves substantially as an isolating and buffer amplifier inwhose output circuit there is fed by way of the conductor I4I a pulse ofnegativepolarity during time intervals when one of the several channelsenergized from the rectifier 65 isto be keyed. Contrasted with thispolarity of output signal, the output from the tube I24'which isconnected by way of the conductor I42 to key another of the series ofimpulses formedfrom the output of the rectifier 65 is of the oppositepolarity, for

a purpose which will be hereinafter made more apparent.

As was above explained the output from the tube I30 while fed tothecontrol electrode I 35 Therefore, the pulse, as it appears in theoutput a tube I22 in theinput circuit of which the capacity element I23and the leak resistor I24 are suitably chosen in value to shape anddelay the impulse as necessary. The widthof the pulse applied upon thecontrol electrode I2I of the tube I22 is controlled and the pulse isnarrowed by this wave shaping and narrowing circuit. The output energyfrom tube I22 is then so connected as to energize a plurality of cascadeconnected of the tube I31 and as it is fed or supplied to the controlelectrode I45 of the tube I46 is of like polarity to that impulse whichappears in the conductor I4I. However, the tube I46 functions again to.invert the polarity of this impulse and in the output circuit of thetube I46 there aptubes I 23 and I24 serving to amplify and isolate theoutput energy from the tube I 22. The output energy from.-the tube I24,wherein appears impulses which occur at the fleldfrequency, hereinaboveassumed for the purpose of convenience, present practice andillustration only as occurring cycles per second, may then ,be' used to.03 andtransformer 61 upo'n the rectifying tube- During the time-periodwhen impulses occur ring at the field frequency of 60 cycles aresupplied to the tube 3' by way of the conductor 55 and the suitablecoupling means, these same imD s are being supplied by way of thecoupling condenser I25 upon the control electrode "I26 of the tube IIIof a second keying channel;

It will be seen from the arrangement indicated that the impulsesoccurring at the field frepears in the conductor I41 an impulse of apolarity opposite that in theconductor MI and of a polarity like thatinthe conductor I42.

It can be seen from the connections shown that the output energy fromthe tube I30 is supplied by way of the conductor I4I to the screenelectrode I49 of the tube 91. Similarly, the output energy from the tube124 s supplied by wayof the conductor I 42 to the screen electrode I50of the tube IIO while theoutput from the tube I46 is fed by way of theconductor I41 to the screen electrode I5I of the tube I I2. The polarityof the signal appearing in the conductors I42 and I 41 o the cathode atthese time periods so that the normal bias (that is, as shown in thepresent case, at ground or cathode reference potential) which issupplied to these tubes to maintain them in an inoperative ornon-conducting state is removed and the pulses of double frequency whichappear in the-output circuits of the tubes 98 and 2,2se,sso

I08 respectively will be caused to energize the common output conductorI55 for all of the tubes 91, H and H2. Each of these tubes 9?, H0 and H2has its anode or plate voltage supplied from a common source by way ofsuitable resistor I51.

In view of the fact that the field frequency impulses supplied to thetube H3, by way of the conductor 55, are delayed, as above described,for a predetermined time interval by delay networks comprising theresistors H5, H6 and condenser I'I'I, it will be seen that thekeyingaction applied to the tube H2 is such that the tube H2 is carried to aconductive state just slightly prior to the time'when the tube IIIlisrendered conductive by reason of its connection through conductor I42 tothe output of the tube I24. However, at the instant when the tube H2becomes conducting by reason of the positive potential applied to itsscreen electrode I5i by way of the conductor I4'I, there is applied tothe screen electrode I49 of the tube 91' by way of the conductor I M apotential which is negative in sign or, in other words, opposite sign tothat applied to the tube II2. Consequently, the tubes 91 and H2 arekeyed in such a manner that'during the time periods when the tube 91 isoperative to pass current the tube H2 is inoperative to draw platecurrent, so that during time periods when the tube H2 is operative, thetube 91 becomes inoperative. I These periods of operation have beenindicated in a relative time relationcondenser I25 and the resistorreason of the parameters chosen for the coupling I25. This is evidentfrom Fig. 2 of the drawing, wherein it ship by the numericaldesig'nations applied to the synchronizing pulses shown in Fig. 2.

It will be seen further that during the period of time of the markedvertical synchronizing pulse interval, certain synchronizing impulses oflonger duration are occurring. These are the impulses due to the keyingprovided by way of the channel including the tubes II3, I20, I22, I23,I24 and conductor I42 serving to supply positive voltage upon the screenelectrode I50 of the tube IIO. It was pointed out above that the timedelay constant for controlling the delay in which the energy in theconductor 55 was supplied to the control electrode I II! to the tube II3 was such as to delay the pulse at the field frequency which issupplied by way of the conductor 55 is of a time indicated by the periodvertical blanking in Fig. 2. However, with the relay of the time whenthis pulse should become effective of the control electrode N8 of thetube H3 being of a time period equal to the first equalizing pulseinterval reading left to right in Fig. 2 the effects of this pulse forkteyiiig purposes will not be realized in this ins an It was pointed outhereinabove, however, that the tube I22 functioned as a pulse narrowingtube and that one of the principal reasons for this narrowing effect isbecause of the'parameters chosen of the resistor I24 and'condenser I23'. This narrowing effect is such that an actually effective timeperiod of the pulse. applied by way of conductor I42 to key the tube IIll is narrowed from the time period normally expected so that itcommences at a time period indicated by the legend marking the beginningof the vertical synchronizing pulse interval. These pulses are thencontinuing until the next time when picture signals are transmitted anduntil such time the actual modulation of the transmitter is only thatgiven and indicated by the vertical synchronizing pulse interval on Fig.2.

Further than this, there is some slight narrow-.

ing eflect which takes place in the keying channel includin's the tubeII4 which becomes efiected by will be seen that the horizontalsynchronizing pulses start prior to the time period when the verticalblanking pulses would normally terminate and at which time the videopicture reproduction again takes place. This then permits the tube 9] totransmit to the common output circuit 555 line frequency impulses whichresult from the sine wave energy applied through conductor 5 53 to thetransformer 61 and the narrowing effect of the vertical blanking isaccording to the schematic illustration of the wave form shown,

equal to the duration of seven picture lines, although there can be areasonable degree of tolerance in this value and the blanking signal maybe of slightly longer duration, in which event the narrowing eifectproduced in'the channel including the tube H3 will have to be stillgreater than above explained for the same number of equalizing impulsesindicated in Fig. 2 of the drawings. It is, of course, apparent that thenumber of equalizing pulses, as well as the vertical pulses is not of aparticularly critical nature but for practical considerations the numberof such values indicated in the present disclosure represents thatnumber which has been found to be most satisfactory for general usage.

Under such conditions and with the tubes 91,

III], HZ all feeding their output into a common energy is thentransferred by way of a coupling condenser III! to be impressed upon theinput or control electrode ill of a tube "2 which functions by reasonof-the bias applied by way of the resistor I73 as a clipping tube. Asindicated by Fig. 2 of the drawings during the entire period representedby the production of the vertical synchronizing pulses, the tube H2 willhave rendered operative by reason of the positive bias applied to thescreen electrode I5I by way of the conductor I41 so that there issuperimposed upon the edge of each of the vertical synchronizing pulsesa pulse substantially like the equalizing pulses indicated immediatelyto the left of the vertical synchronizing pulses in Fig. 2. The tube HZ,therefore, functions to clip this pulse from the vertical impulse sinceit is of no material use in thesynchronizing control exercized upon thereceiver. The output from the tube I12 may then be fed to a tube ofsubstantially similar characteristics except that it is arranged to clipthe impulse in the opposite direction. The output energy from the tubeH2 is then supplied by way of the conductor I14 and the couplingcondenser Il5 to the output terminal H6, from which it is introducedinto a selected television transmitter where the picture synchronizingand blanking signals are mixed. There practically has been suggesteddiifererlt points in the transmitter in which this signal may beintroduced but for practical purposes the combined signal may beintroduced in one'of the amplifier stages preceding the modulation or inmany instances should be introduced promptly into the modulator.

From what has been above described it is apparent that manymodifications and changes may be made in the arrangement and circuitdisclosed and it is, therefore, contemplated that any and all suchmodifications and changes which fall fairly within the spirit and scopeof the invention as hereinafter claimedqnay readily be made 6 1 assistedI of line traces and repeated at a predetermined without departing fromthat subject matter herein described.

I claim:

1. A'system for producingline and frame synchronizing impulses for usein a television system comprising means for producing a substantiallysine wave of .electrical energy at linev repetition frequency, means forderiving-impulses of line synchronizing frequency from successive halvesof like polarity of said produced sine wave, means for deriving fromeach half of said produced sine wave without regard to polarity asuccession of uniform impulses at twice repetition rate of thefirst'named produced impulses, means to produce a first series ofimpulses of frame synchronizing frequency, means to'produce a secondseries of I .impulses of frame synchronizing frequency delayed withrespect to said first series of impulses of frame synchronizingfrequency, and means to control the transmission of the impulses of linesynchronizing frequency and the impulses of twice line synchronizingfrequency by the first and second series of impulses of frame synchronizing frequency. 1 2. A system for producing line and framesynchronizing impulses for use in a television system comprising anelectronic oscillator producing substantially sine waves of electricalenergy at a predetermined line repetition frequency, electronic waveshaping means for deriving impulses of line synchronizing frequency fromsuccessive halves of like polarity of said produced sine waves, meansfor deriving from each half of said produced sine wave withoutregard topolarity a plurality of successions of uniform impulses at twice therepetition rate of the first named produced impulses, means to producetwo series of impulses of frame synchronizing frequency, said two seriesof impulses being displaced in phase relationship by a predeterminedamount,

and means to control the transmission of the impulses of linesynchronizing frequency and the impulses of twice line synchronizingfrequency by the two series of impulses of frame synchronizingfrequency.

3. A system for producing line and frame synchronizing impulses for usein a television system comprising oscillator means for producingasubstantially sine wave of electrical energy at line repetitionfrequency, wave shaping means for deriving impulses of linesynchronizing frequency pattern repetition rate from alternating fieldsin a television system comprising, means for producing substantiallysine wave oscillations at a frequency corresponding to the linerepetition rate, means for producing line synchronizing impulses fromsuccessive halves of like polarity of the developed sine waves, meansfor producing impulses at twice the line frequency from each of theproduced sine waves by inverting alternate halves of the sine waves toproduce impulses of substantially uniform configuration and polarity,means to produce under the control of the sine wave oscillation impulsesof a frequency 'corresponding to the field repetition rate, a keyingcircuit, means for energizing the keying circuit by said field frequencyenergy, means controlled by the keying circuit for combining theimpulses produced at line frequency and at twice the line frequencyalternately and successively, and an output circuit for all of saidimpulses.

. 5. A synchronizing system for producing interlaced electro-opticalpatterns each of a predeterfromsuccessive halves of like polarity ofsaid producedsine wave, a full .wave rectifier means,

vmeans for deriving from the rectified alternating halves of saidproduced sine wave a succession of uniform impulses at twice the linesynchronizing frequency, means for producing two series of impulses offrame synchronizing frequency,

said two series of impulses being phase displaced by a predeterminedamount, and means to control the transmissionhof. the impulsesof linesynchronizlng frequency and the impulses of twice line synchronizingfrequency by the two series of impulses of, frame synchronizingfrequency.

4.1 system for producing synchronizing impulses for controlling theproduction of electrooptical patterns each of a predetermined numbermined number of line traces and repeated at a predetermined patternrepetition rate from alternating fields in a television systemcomprising means for producing substantially sine wave oscillations at afrequency corresponding to the line repetition rate, means for producingline synchronizing impulses from successive halves of like polarity ofthe developed sinewaves, means for producing impulses at twice the linefrequency from each of the produced sine waves by inverting alternatehalves of the sine waves to produce impulsesof substantially uniformconfiguration and polarity, means to produce under the control of thesine wave oscillations impulses of a frequency corresponding to thefieldrepetition rate, and means for alternately 40 and sequentiallycombining the impulses produced at line frequency and at twice the linefrequency under the control of the impulses produced at field frequency.

6. The method of developing synchronizing signals for producinginterlaced electro-optical patterns each of a predetermined number ofline traces repeated at a predetermined pattern repetition rate fromalternating fields in a television system comprising the steps ofproducing substantially sine wave oscillations at a frequencycorresponding to the line repetition rate, producing synchronizingimpulses at the line repetition frequency from successive halves of likepolarity of the developed sine waves, inverting alternate halves of thesine Waves to produce impulses of substantially uniform configurationand polarity to produce impulses at twice the line frequency from eachof the produced sine waves, generating from the sine wave oscillationsimpulses of a frequency corresponding to the field repetition rate, andalternately and sequentially combining the impulses produced at linefrequency and at twice the line frequency under the controlof theimpulses produced at the field repetition rate.

' STUART W. SEELEY.

